彻底重构状态系统：整合所有旧状态到 MainGraphState，修复所有节点

backend/app/main_graph/nodes/memory_trigger.py

@@ -1,18 +1,10 @@
 from typing import Any, Dict
 from langchain_core.runnables.config import RunnableConfig
-from app.main_graph.state import MessagesState
+from app.main_graph.state import MainGraphState
 from app.memory.mem0_client import Mem0Client
 from app.logger import info
 
 
-def _get_attr(state, attr_name, default=None):
-    """通用方法：兼容 dict 和 dataclass 两种状态格式"""
-    if isinstance(state, dict):
-        return state.get(attr_name, default)
-    else:
-        return getattr(state, attr_name, default)
-
-
 # 全局变量，在 GraphBuilder 中注入
 _mem0_client: Mem0Client = None
 
@@ -22,12 +14,12 @@ def set_mem0_client(client: Mem0Client):
     _mem0_client = client
 
 
-async def memory_trigger_node(state, config: RunnableConfig) -> Dict[str, Any]:
+async def memory_trigger_node(state: MainGraphState, config: RunnableConfig) -> Dict[str, Any]:
     """检测用户消息中的记忆指令，若命中则主动调用 Mem0 存储"""
     if _mem0_client is None:
         return {}
 
-    messages = _get_attr(state, "messages", [])
+    messages = state.messages
     if not messages:
         return {}